Decompression illness (DCI) encompasses decompression sickness (DCS) and arterial gas embolism. The term decompression illness refers to inert bubble-induced dysbaric disease regardless of the location of the bubbles, which may be in the tissues or in the intravascular spaces. The bubbles arise due to a rapid drop in atmospheric pressure or due to pulmonary barotrauma.

Epidemiology

Decompression illness can occur in:

• divers if ascent to the surface is too rapid

  • the reported incidence in sports divers is 3 in 10,000 dives

  • in commercial divers the incidence is up to 10 in 10,000 dives

• workers leaving a caisson (pressurised chamber)

• during unpressurised flight to high altitude

• extra-vehicular activity in space

Clinical presentation

Symptoms depend on the location of the bubbles, and vary from mild to severe:

• bone and/or muscle pain, typically in the shoulders, and less frequently in the elbows, knees or ankles

• headache and focal neurological deficits, such as paralysis, visual disturbances or vertigo

• death

For a further discussion please see decompression sickness.

Pathology

According to Henry's Law, the solubility of a gas in a liquid is proportional to the partial pressure of a gas over the liquid. For divers, pressure increases by one atmosphere for every additional 10.06 metres in depth, causing more gas to be dissolved in blood and body fluids. Oxygen is metabolised, but gases like nitrogen and helium accumulate. On ascent these gases leave solution and the gas bubbles expand. If ascent is too rapid this causes decompression illness.

Pulmonary barotrauma can occur during diving descent (lung squeeze) or ascent (pulmonary overinflation syndrome). Gas can enter lung parenchyma or vessels through tears and can cause arterial gas embolism.

Bubbles can block vessels, cause spasm or cause endothelial damage which activates both the clotting cascade and inflammatory mediators leading to increased permeability, oedema and ischaemia.

Radiographic features

Chest radiograph is important to exclude pneumothorax prior to treatment in a hyperbaric chamber.

For further discussion please see decompression sickness.

Treatment and prognosis

General treatment options include:

• FiO₂ 100% oxygen

• hyperbaric chamber if there is no inner ear barotrauma

See also

• cerebral air embolism